i40e: Implement an ethtool private flag to stop LLDP in FW

Implement the private flag disable-fw-lldp for ethtool
to disable the processing of LLDP packets by the FW.
This will stop the FW from consuming LLDPDU and cause
them to be sent up the stack.

The FW is also being configured to apply a default DCB
configuration on link up.

Toggling the value of this flag will also cause a PF reset.

Disabling FW DCB will also disable DCBx.

Signed-off-by: Dave Ertman <david.m.ertman@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>